This is my switch-case script:
switch ($_GET['page'])
{
case '?users':
.....
default: echo 'Welcome';
}
This script work fine but when i load page first time he return error:
Notice: Undefined index: page in
I know why because script does't knows what value is. How to set default value and avoid error?
1a) Check the index page exists
if( array_key_exists('page', $_GET) ) {
}
1b) Set a default value
$_GET['page'] = array_key_exists('page', $_GET) ? $_GET['page'] : '';
2) Your case statement is incorrect
case 'users' :
//...
break;
3) All the code together
$_GET['page'] = array_key_exists('page', $_GET) ? $_GET['page'] : '';
switch ($_GET['page']) {
case 'users':
//...
break;
default:
echo 'Welcome';
break;
}
Tips
Make sure you break; the case block.
Always check indexes are there before blindly using them
use isset():EDITED
if(isset($_GET['page'])){
switch ($_GET['page'])
{
case 'users':
.....
default: echo 'Welcome';
}
}
Related
For the following php program with a switch statement, why '' give me $vSS=2 instead of =1?
Quite strange to me. I am using PHP 5.5.9.
I can add case '': to resolve the problem, but I am curious why PHP give $vSS=2 instead of
$vSS=1. Is it normal or a bug?
<?php
R(15); // 1 ok
R(''); // why give me 2
R(40); // 2 ok
R(70); // 3 ok
#
function R($SS){
switch($SS){
case $SS<=20: $vSS=1;break;
case ($SS>20 and $SS<=49.9): $vSS=2; // why here?
if($SS == '') echo "DEBUG: SS is a null string.<br>\n";
break;
case ($SS<=100 and $SS>49.9): $vSS=3; break;
default:$vSS=0 ;
}
echo "DEBUG:(SS/vSS) $SS:$vSS\n";
}
?>
------ RESULT
DEBUG:(SS/vSS) 15:1
DEBUG: SS is a null string.<br>
DEBUG:(SS/vSS) :2
DEBUG:(SS/vSS) 40:2
DEBUG:(SS/vSS) 70:3
You don't understand how switch works. It compares the value in switch($SS) with each of the case values, it doesn't just test each case. So
switch ($SS) {
case $SS<=20:
is similar to:
if ($SS == ($SS<=20))
The reason the second case is being executed is because ($SS > 20 && $SS <= 49.9) is false, and false is considered equal to zero or an empty string.
You shouldn't use switch for what you're doing, you should use if/then/elseif/else:
if ($SS <= 20) {
$vSS = 1;
} elseif ($SS <= 49.9) {
$vSS = 2;
} else {
$vSS = 0;
}
#Barmar is right, expression in case() is compared to switch(something_here) but you don't have to cahnge your all your code to if/elsif/elsif/.../... logic. Just change switch() statement to true
switch(true) { // <-- this part only
case $SS<=20:
$vSS=1;
break;
case ($SS>20 and $SS<=49.9):
$vSS=2; // why here?
// must not be here
// if($SS == '') echo "DEBUG: SS is a null string.<br>\n";
break;
case ($SS<=100 and $SS>49.9):
$vSS=3;
break;
case $SS=='': // you can check it here
echo "DEBUG: SS is a null string.<br>\n";
break;
default:
$vSS=0 ;
}
I have a switch statement set up which checks the value in an array field. I also want to perform slightly different logic if the array has no field with that name.
I can write the code like this, which works, but looks a little messy in my mind:
if (!isset($_GET['action']))
{
require('menu.html');
}
else
{
switch ($_GET['action'])
{
case 'debug':
require('core/actions/debug.php');
break;
case 'submit':
require('core/actions/submit.php');
break;
case 'admin':
header("Location: /login");
break;
}
}
But would it be possible for me to instead move the logic from the if statement and combine it with with my switch logic?
In JavaScript, I could do case undefined: ... as just one of the cases. Can I do something similar in PHP?
If $_GET['action'] is empty, or does have value, but its not any of the ones you want, you can do this.
switch ($_GET['action'])
{
.............
case "":
echo "empty or not setted";
break;
}
But if $_GET['action'] is not setted it will throw notices on every comparison (but it will enter in case '' anyway).
To not show the notices you could do:
switch (#$_GET['action'])
But please, don't do that!
You could do the super-switch-crazy way too:
switch(true){
case !empty($_GET['action']):
switch ($_GET['action'])
{
.............
}
break;
default:
echo "not setted or empty";
break;
}
Edit:
As #IQAndreas pointed out in the comments a interest solution could be:
switch (true)
{
case (!isset($_GET['action']):
require('menu.html');
break;
case ($_GET['action'] == 'debug'):
require('core/actions/debug.php');
break;
case ($_GET['action'] == 'submit'):
require('core/actions/submit.php');
break;
case ($_GET['action'] == 'admin'):
header("Location: /login");
break;
}
But the best way IMO to handle this situation is doing what you are already doing (checking if the var is empty or setted, before the switch..case)
if (isset($_GET['action'])){
switch ($_GET['action'])
{
.............
case "":
echo "empty";
break;
}
} else {
echo "not setted";
}
--Let me add this. This code works for me the way it is. I just do not know why it works.--
I can't figure this out.
switch ($_SERVER['QUERY_STRING']) {
case isset($_GET['test0']):
echo "test0<br>";
break;
case isset($_GET['test1']):
echo "test1<br>";
break;
case isset($_GET['test2']):
echo "test2<br>";
break;
case isset($_GET['test3']):
echo "test3<br>";
break;
case isset($_GET['test4']):
echo "test4<br>";
break;
default:
echo "no test<br>";
break;
}
When the url is index.php?test0, "test0" is shown.
When the url is index.php?test4, "test4" is shown.
When the url is index.php?test999, "no test" is shown.
When the url is index.php?tes, "no test" is shown.
When the url is index.php?, or index.php, "test0" is shown.
Why is this? The condition is not met, so should the default not be shown?
switch can't be used this way. isset() returns true or false, not something (a string, an int, etc) you can match against. What you are basically doing is:
switch ($_SERVER['QUERY_STRING']) {
case true:
echo "test0<br>";
break;
case true:
echo "test1<br>";
break;
case false:
echo "test2<br>";
break;
case false:
echo "test3<br>";
break;
case true:
echo "test4<br>";
break;
default:
echo "no test<br>";
break;
}
cases are considered from top to bottom. In this case, $_SERVER["QUERY_STRING"] is automatically type-converted to bool (which will return true in this case). The first case it sees would be test0, so it echos that. If you do that for test0-4, it will give you the false illusion that this code is working as intended, while it's not considering the edge cases.
The only way you can achieve what you want is by using multiple ifs, or by redesigning your application.
When the url is index.php?, or index.php, "test0" is shown.
Why is this? The condition is not met, so should the default not be shown?
Like a good question, your question as well contains the answer already.
You already have realized that the condition must be met even you think it is not met. Therefore you ask. So let's see which condition is met:
case isset($_GET['test0']):
echo "test0<br>";
break;
This is a test for isset($_GET['test0']) and we know with the request that this is FALSE. So this test tests for FALSE.
Now let's see against what this tests:
switch ($_SERVER['QUERY_STRING']) {
That is $_SERVER['QUERY_STRING']. So if $_SERVER['QUERY_STRING'] is FALSE the test0 will be output.
Because switch { case:} in PHP does loose comparison, the empty string $_SERVER['QUERY_STRING'] is FALSE. This is why you see the output.
Easy if you know why, right? And all so logical.
And what you wanted to test against was not $_SERVER['QUERY_STRING'] but just TRUE:
switch (TRUE)
{
case isset($_GET['test0']) :
...
}
This gets the job done, too.
<?php
$q = $_SERVER['QUERY_STRING'];
if(!empty($q) && isset($q) && strlen($q) >0 ){
$url = $q;
switch ($url){
case true;
echo $url;
break;
}
}
else {
echo "no test<br>";
}
what about
$found = false;
for($i=0;$i <=4; $i++){
if( isset($_GET['test'.$i]) ){
echo "test".$i;
$found = true;
}
}
if(!$found){
echo "no test";
}
$door = $_POST["doorType"];
$doorWidth;
if ($door=="Single")
{
$doorWidth = $width;
}
else if ($door=="Double")
{
$doorWidth = $dOneWidth;
}
When I run the page it doesn't recognize the variable $doorWidth?
$doorWidth;
doesn't assign anything. It only returns the variable ... to anything. Doing this PHP is accessing the variable, causing a notice. Write for example:
$doorWidth = NULL; // assigns something (some default value if $door isn't "Signle" nor "Double")
I guess that $door has a value far from Single|Double. This may be caused by another error in your application. You should learn, that you should in any case set a proper default value for a variable if you are about to assign to it from into a conditional statement (like if):
$doorWidth = 'not set!';
if ($door=="Single")
{
$doorWidth = $width;
}
else if ($door=="Double")
{
$doorWidth = $dOneWidth;
}
Further note about the switch statement which has a default: branch:
switch($door) {
case 'Single' :
// do something
break;
case 'Double' :
// do something else
break;
default:
die('$door has a value far from 'Single|Double'. Currently: ' . $door);
}
I have a bit of a problem with my PHP code, I am assigning values to variables in different states of the flow depending on what I receive, but for some reason it keeps getting stuck at one point, here is the code.
if (isset($session)) {
//if the user is in the database
if ($row == 1) {
$from = $_GET['from'];
if (isset($from)) {
$page = $_GET['page'];
switch ($page) {
case "game":
$page = "game";
sendVars($page);//send the variable
break;
case "gallery":
$page = "gallery";
sendVars($page);//send the variable
break;
case "leaderboard":
$page = "leaderboard";
sendVars($page);//send the Variable
break;
}
}else {
$page = "game";
sendVars($page);//send the variable
}
//if the user is not in the database
}else {
//do this
}
} else {
//register
}
Now for some odd reason, it keeps setting the value of $page to game, even though I set the page variable to gallery like so http://www.mydomai.com/?from=set&page=gallery . the only reason for this that I can think of is that my switch is not working as it should? or it is bypassing the switch somehow?
Thanx in advance!
I just ran your code after removing a few of the unessersary variable assignments:
<?php
// I added this function just for testing
function sendVars($page) {
echo $page;
}
if (isset($_GET['from'])) {
$page = $_GET['page'];
switch ($page) {
case "game":
sendVars($page); //send the variable
break;
case "gallery":
sendVars($page); //send the variable
break;
case "leaderboard":
sendVars($page); //send the Variable
break;
}
} else {
$page = "game";
sendVars($page); //send the variable
}
And it all seems fine, xxx.php?from=1&page=gallery echos out "gallery", try doing a print_r($_GET) at the top of your script and see what it prints out and let us know.
On a side note I think the below may be shorter for you and still do the same thing:
if (isset($_GET['from'])) {
// Check if $_GET['page'] exsists and is either game, gallery or leaderboard
if (isset($_GET['page']) && in_array($_GET['page'], array('game', 'gallery', 'leaderboard')))
sendVars($_GET['page']);
}
else
sendVars('game');
I hope this helps
Cheers
Luke
Try doing a var_dump($page);exit; before the switch and see what it spits out.
Also you can do a var_dump($from) and see what that is spitting out - it may be that it goes to the else, so it may not even be getting to the switch.
If this is inside a function, I personally prefer guard-style clauses than constantly increasing the levels of indentation. The idea is you pick out the bad conditions (ie if something is going wrong) to "protect" the larger block of logic.
In your case that's the switch statement.
if (!isset($session))
return ...; // register
if ($row != 1)
return ...; // do this
$from = $_GET['from'];
$page = $_GET['page'];
if (isset($from)) switch ($page) {
case "game":
$page = "game";
break;
case "gallery":
$page = "gallery";
break;
case "leaderboard":
$page = "leaderboard";
break;
}
else $page = "game";
return sendVars($page);// don't need to repeat this if all cases do it!
It's just a style of code and it's not going to fix all (if any) of your problems. You actually don't need the switch block in there for this code. I can't see that it's doing anything.
You don't necessarily need the switch statement. I can't see an obvious problem with your logic but I think this will do the same thing:
if (isset($session))
{
//if the user is in the database
if ($row == 1)
{
$page = (in_array($_GET['page'],array('game','gallery','leaderboard'))) ? $_GET['page'] : "game";
sendVars($page); //send the variable
}
else //if the user is not in the database
{
//do this
}
}
else
{
//register
}
Just saw Luke used the same in_array method but 25 mins before me. Serves me right for being slow!